Catheter Shaft and Method of Its Manufacture

ABSTRACT

A method of manufacturing a catheter shaft includes the steps of forming an inner layer of a first polymeric material, forming a plait matrix layer including a second polymeric material about the inner layer, and forming an outer layer of a third polymeric material about the plait matrix layer. The plait matrix layer includes a braided wire mesh partially or fully embedded within the second polymeric material, which is different from at least one of the first polymeric material forming the inner layer and the third polymeric material forming the outer layer. The second polymeric material has a higher yield strain and/or a lower hardness than at least the first polymeric material, and preferably both the first and the third polymeric materials. The first polymeric material and the third polymeric material may be different or the same. The catheter shaft may be formed by stepwise extrusion, co-extrusion, and/or reflow processes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/963,813, filed 26 Apr. 2018, now pending (“the '813 application”),which is a continuation of U.S. application Ser. No. 15/140,750, filed28 Apr. 2016, now U.S. Pat. No. 9,987,463 (“the '750 application), whichis a continuation of U.S. application Ser. No. 13/795,647, filed 12 Mar.2013, now U.S. Pat. No. 9,352,116 (“the '647 application”), which is adivisional of U.S. application Ser. No. 11/967,220, filed 30 Dec. 2007,now U.S. Pat. No. 8,431,057 (“the '220 application”). This applicationis also related to U.S. application Ser. No. 11/967,219, filed 30 Dec.2007 (“the '219 application”). The '813, 750, '647, '220, and '219applications are hereby incorporated by reference as though fully setforth herein.

BACKGROUND

The instant invention relates to catheters that are used in the humanbody. In particular, the instant invention relates to catheters using ahyperelastic plait matrix to improve the kink resistance andmaneuverability of the catheter.

Catheters are used for an ever-growing number of procedures. Forexample, catheters are used for diagnostic, therapeutic, and ablativeprocedures, to name just a few examples. Typically, the catheter ismanipulated through the patient's vasculature and to the intended site,for example, a site within the patient's heart. The catheter typicallycarries one or more electrodes, which may be used for ablation,diagnosis, or the like.

Since the path through the patient's vasculature to the intended site isoften long and tortuous, steering forces typically must be transmittedover relatively great distances. Accordingly, it is desirable for acatheter to have sufficient axial (e.g., column) strength to be pushedthrough the patient's vasculature via a force applied at its proximalend (“pushability”). It is also desirable for a catheter to transmit atorque applied at the proximal end to the distal end (“torqueability”).Pushability and torqueability (collectively, “maneuverability”) permit aphysician to manipulate a catheter to an intended site and then properlyorient the catheter. It is also desirable for a catheter to havesufficient flexibility to substantially conform to the patient'svasculature and yet resist kinking as it does so. Kinking is often theresult of a localized failure of the material of the catheter whenlocalized stresses exceed the yield strength of the material.

To provide pushability, torqueability, flexibility, and kink resistance,many extant catheters are made of engineering polymer materialsreinforced with metallic wire braiding plaits. The characteristics ofpushability, torqueability, flexibility, and kink resistance are oftenin tension with one another, however, with improvements in one requiringcompromises in others.

BRIEF SUMMARY

It is desirable to provide a catheter with improved flexibility, kinkresistance, and maneuverability.

It is also desirable to provide a catheter with improved mechanicalintegrity.

In a first aspect, the present invention provides a method ofmanufacturing a catheter shaft, generally including the following steps:forming an inner layer of a first melt-processable polymer; forming aplait matrix layer about the inner layer, the plait matrix layerincluding a braided wire mesh embedded (e.g., partially or fullyembedded) in a matrix material layer including a second melt-processablepolymer; and forming an outer layer of a third melt-processable polymerabout the plait matrix layer, wherein the second melt-processablepolymer forming the matrix material layer is different from at least oneof the first melt-processable polymer and the third melt-processablepolymer. Optionally, the braided wire mesh may be coated with silicone.

Typically, the matrix material (e.g., the second melt-processablepolymer) will be hyperelastic relative to at least the firstmelt-processable polymer, and will preferably be hyperelastic relativeto both the first melt-processable polymer and the thirdmelt-processable polymer (for example, where the first and secondmelt-processable polymers are the same). The yield strain of the matrixmaterial is preferably between about 3% and about 100%, and morepreferably between about 5% and about 50%. Suitable materials for thematrix material include styrenic block copolymers (e.g., Kraton®),functionalized thermoplastic olefins, thermoplastic elastomeric alloys,thermoplastic polyurethanes (e.g., Estane®, Pellethane®),polyamide-based thermoplastic elastomers (e.g., Pebax®), polyester-basedthermoplastic elastomers (e.g. Hytrel®), ionomeric thermoplasticelastomers (e.g., Surlyn®), and any combinations thereof. The Shorehardness of the matrix material may be between about 10D and about 85D,more preferably between about 20D and about 70D.

In some aspects of the invention, the plait matrix layer is formed aboutthe inner layer by braiding the wire mesh about the inner layer to forma reinforced inner layer and then extruding the matrix material aboutthe reinforced inner layer to form the plait matrix layer. Similarly,the outer layer may be formed about the plait matrix layer by extrudingthe third material to form the outer layer about the plait matrix layer.It is also contemplated that the matrix material and the third materialmay be co-extruded to concurrently form the plait matrix layer and theouter layer.

In other aspects of the invention, the inner layer, the plait matrixlayer, and the outer layer are heated to bond the inner layer, the plaitmatrix layer, and the outer layer together, thereby forming a unitarycatheter shaft. A heat-shrink tube may be introduced about the outerlayer prior to the heating step.

Also disclosed herein is a method of forming a catheter shaft, includingthe steps of: forming an inner layer of a first material; and forming aplait matrix layer about the inner layer, the plait matrix layerincluding a braided wire mesh at least partially embedded within asecond material, wherein the second material is hyperelastic relative tothe first material. An outer layer of a third material may optionally beformed about the plait matrix layer. At least one of the first materialand the second material may include a radiopaque filler material.

The step of forming a plait matrix layer will typically include formingthe braided wire mesh about the inner layer; and impregnating thebraided wire mesh with the second material. The braided wire mesh may beformed about the inner layer by braiding the wire mesh about the innerlayer or by braiding the wire mesh about a core, decoring the braidedwire mesh, and placing the braided wire mesh about the inner layer.Similarly, the braided wire mesh may be impregnated with the secondmaterial by forming a layer of the second material about the braidedwire mesh and heating the layer of the second material to flow andimpregnate the braided wire mesh or by extruding a layer of the secondmaterial about the braided wire mesh.

In another aspect, the present invention provides a catheter shaftformed according to a method including the steps of: forming an innerlayer of a first melt-processable polymer; forming a plait matrix layerabout the inner layer, the plait matrix layer including a braided wiremesh embedded in a matrix material layer of a second melt-processablepolymer; and forming an outer layer of a third melt-processable polymerabout the plait matrix layer, wherein the matrix material ishyperelastic relative to at least one of the first melt-processablepolymer and the third melt-processable polymer.

In still another aspect of the present invention, a catheter shaftincludes: an inner layer of a first polymeric material; and a plaitmatrix layer bonded to the inner layer, the plait matrix layer includinga braided wire mesh embedded in a second polymeric material, wherein thesecond polymeric material is hyperelastic relative to the firstpolymeric material. The catheter shaft may also include an outer layerof a third polymeric material bonded to the plait matrix layer. Thethird polymeric material forming the outer layer is optionally the sameas the first polymeric material forming the inner layer.

In still another aspect of the present invention, a catheter shaftincludes: an inner layer of a first polymeric material; a plait matrixlayer bonded to the inner layer, the plait matrix layer including abraided wire mesh embedded in a second polymeric material; and an outerlayer of a third polymeric material. The second polymeric material ishyperelastic relative to both the first polymeric material and thesecond polymeric material.

In still another aspect of the present invention, a catheter shaftincludes: an inner layer of a first polymeric material; a plait matrixlayer bonded to the inner layer, the plait matrix layer including abraided wire mesh embedded in a second polymeric material; and an outerlayer of a third polymeric material. The first material forming theinner layer and the third material forming the outer layer are selectedto have sufficiently high mechanical strength and rigidity for shaftmaneuverability. The first material and the third material may bedifferent materials or the same material, and are typically selectedfrom the group consisting of thermoplastics, including polyesters,polyamides, polycarbonate, polysulfones, polyimides, polyketones, liquidcrystal polymers, functionalized polypropylene and copolymers or anycombinations of the above, or high performance engineering thermoplasticelastomers with a durometer of at least about 60D, includingpolyester-based thermoplastic elastomers, polyamide-based thermoplasticelastomers, thermoplastic polyurethanes, and the like.

An advantage of the present invention is that it provides a catheterhaving increased flexibility and kink resistance.

Another advantage of the present invention is that it enhancesmechanical integrity of the catheter with increased torqueability andcolumn strength, as well as pushability.

The foregoing and other aspects, features, details, utilities, andadvantages of the present invention will be apparent from reading thefollowing description and claims, and from reviewing the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an exemplary catheter according to anembodiment of the present invention.

FIG. 2 is an axial cross-sectional view of the various components of acatheter shaft assembly according to an embodiment of the presentinvention prior to the application of energy to melt process thecatheter shaft assembly.

FIG. 3 is a longitudinal cross-sectional view of the various componentsof a catheter shaft assembly according to an embodiment of the presentinvention prior to the application of energy to melt process thecatheter shaft assembly.

FIG. 4 is an axial cross-sectional view of a catheter shaft assemblyaccording to an embodiment of the invention during the application ofenergy to melt process the catheter shaft assembly.

FIG. 5 is an axial cross-sectional view of a catheter shaft according toan embodiment of the invention after the application of energy to meltprocess the catheter shaft assembly into the catheter shaft.

DETAILED DESCRIPTION

The present invention provides a catheter shaft suitable for use in thehuman vasculature for known medical procedures, such as cardiac mappingand ablation. Catheters utilizing catheter shafts according to thepresent invention advantageously exhibit improved maneuverability,flexibility, and kink resistance. For purposes of this description, theinvention will be described in connection with an elongateelectrophysiology catheter. It is contemplated, however, that thedescribed features and methods may be incorporated into any number ofcatheters (e.g., steerable catheters, introducer catheters, and thelike) as would be appreciated by one of ordinary skill in the art.

Referring now to the figures, and in particular to FIG. 1, anelectrophysiology catheter 10 includes a shaft 12 having a distal end 14and a proximal end 16. A handle 18 may be coupled to proximal end 16 ofshaft 12 to control catheter 10 (e.g., to push and/or torque catheter10). Catheter 10 may also include a hub 20 operably coupled to an innerlumen (not shown) within handle 18. A valve 22 may be operably connectedto hub 20. Of course, it is also contemplated that any known device formanipulation of catheter 10 may be coupled to proximal end 16 thereof,including, without limitation, robotic manipulation devices and thelike.

The basic method of manufacture of catheter 10, and in particular of atleast a portion of shaft 12, according to an embodiment of the presentinvention will be described with reference to FIGS. 2-5. As they areassembled, the catheter components will be collectively referred to as a“catheter shaft assembly.”

As depicted in FIG. 2, a mandrel or hypotube 24, which is preferablyround in cross-section and preferably from about 6 inches to about 4feet in length, is a component of the catheter shaft assembly, and maybe the first component thereof during manufacture of catheter shaft 12.Typically, mandrel 24 is disposable. Mandrel 24 has a distal end and aproximal end. An inner layer 26 is formed about mandrel 24. For example,inner layer 26 may be knotted at one end (e.g., the distal end) and thenfed onto mandrel 24.

Inner layer 26 may be an extruded polymeric tubing, such as pre-extruded(and optionally chemically-etched) polytetrafluoroethylene (PTFE) tubing(e.g., Teflon® brand tubing). Inner layer 26 may also be made of othermelt-processable polymers, including, without limitation, fluorinatedethylene-propylene copolymer (FEP), perfluoroalkoxyethylene (PFA),poly(vinylidene fluoride), poly(ethylene-co-tetrafluoroethylene), andother fluoropolymers with surface treatment such as chemical etching,plasma and corona treatment, and the like. One of ordinary skill willalso appreciate that the inner layer 26 may be made of somemelt-processable thermoplastic elastomeric polymers with sufficientlyhigh mechanical strength and rigidity (e.g., durometer of at least about60D), including, without limitation, polyamide-based thermoplasticelastomers (namely poly(ether-block-amide), Pebax®), polyester-basedthermoplastic elastomers (e.g., Hytrel®), thermoplastic polyurethanes(e.g., Pellethane®, Estane®), ionic thermoplastic elastomers,functionalized thermoplastic olefins and any combinations thereof. Ingeneral, suitable materials for inner layer 26 may also be selected fromvarious thermoplastics, including, without limitation, polyamides,polyurethanes, polyesters, functionalized polyolefins, polycarbonate,polysulfones, polyimides, polyketones, liquid crystal polymers and anycombination thereof. Specific suitable materials for inner layer 26include, without limitation, Pebax® 7233, Pebax® 6333, Grilamid L25,Rilsan AESNO, Rilsan BESNO, Makrolon 3108, Makrolon 1239, and the like.

A plait matrix layer including a braided wire mesh assembly 28 and asecond polymeric material layer 30 (also referred to herein as “matrixmaterial layer 30,” and the polymeric material therein as “matrixmaterial”) may then be formed about inner layer 26. Braided wire meshassembly 28 may be formed of stainless steel wire, including, forexample, 0.003″ high tensile stainless steel wire. Braided wire meshassembly 28 may be formed in a standard braid pattern and density, forexample, about 16 wires at about 45 to about 60 picks per inch (“PPI”)density. Alternatively, a braid may be used that is characterized by avarying braid density. For example, braided wire mesh assembly 28 may becharacterized by a first braid density at proximal end 16 of cathetershaft 12 and then transition to one or more different braid densities asbraided wire mesh assembly 28 approaches distal end 14 of catheter shaft12. The braid density at distal end 14 may be greater or less than thebraid density at proximal end 16. In a specific example, the braiddensity at proximal end 16 is about 50 PPI and the braid density atdistal end 14 is about 10 PPI. In another embodiment, the braid densityat distal end 14 is about 20% to about 35% of the braid density atproximal end 16.

Braided wire mesh assembly 28 may be formed separately on a disposablecore and slipped about inner layer 26. Alternatively, braided wire meshassembly 28 may be braided directly upon inner layer 26 to form areinforced inner layer. In addition, one or more portions of braidedwire mesh assembly 28 may be heat tempered and cooled beforeincorporation into the catheter shaft assembly through methods that areknown to those of ordinary skill in the art. The action of heattempering may help to release the stress on the wire and help reduceradial forces.

Matrix material layer 30 may then be formed about braided wire meshassembly 28. In some embodiments of the invention, matrix material layer30 is extruded about the reinforced inner layer (that is, about braidedwire mesh assembly 28) to form the plait matrix layer. In otherembodiments of the invention, matrix material layer 30 is separatelyextruded and then slipped about braided wire mesh assembly 28 as part ofthe catheter shaft assembly.

Preferably, matrix material layer 30 will be of a different materialthan inner layer 26. In particular, in some embodiments of theinvention, matrix material 30 will be hyperelastic relative to innerlayer 26. That is, matrix material layer 30 (and therefore the plaitmatrix layer, as described in further detail below) may have a lowerflexural modulus and a higher yield strain than inner layer 26. Thelower flexural modulus and higher yield strain of matrix material layer30 relative to inner layer 26 advantageously promotes maneuverabilityand kink resistance of catheter shaft 12. Typically, the yield strain ofmatrix material layer 30 will be between about 3% and about 100%, andmore preferably between about 5% and about 50%.

Suitable materials for matrix material layer 30 may be selected fromvarious thermoplastic elastomer resins, including, without limitation,styrenic block copolymers (e.g., Kraton D (includingstyrene-butadiene-styrene (SBS) triblock copolymers andstyrene-isoprene-styrene (SIS) triblock copolymers); Kraton G (includingstyrene-ethylene/butylene-styrene copolymers andstyrene-ethylene/propylene-styrene (SEPS) copolymers; and SIBStarstyre-isobutylene-styrene triblock copolymers), thermoplastic olefins(TPO) and elastomeric alloys (e.g., Santoprene and Versaflex),thermoplastic polyurethanes (e.g., Pellethane; Estane; Tecoflex;Tecothane; Carbothane; Tecoplast; and Tecophilic TPUs),poly(ether-b-amide)s (e.g., Pebax®; Vestamid® E; and Grilamide® ELY),poly(ether-ester)s (e.g., Hytrel), ionomeric thermoplastic elastomers(e.g., Surlyn), and any combinations thereof. Particularly suitablematerials for matrix material layer 30 include, without limitation,Pebax® 4033, Pebax® 5033, Pellethane 2363-55D, and Surlyn 9320.

In some embodiments of the invention, matrix material layer 30 forms theoutermost layer of catheter shaft 12. Alternatively, an outer layer 32may be formed about the plait matrix layer (that is, about matrixmaterial layer 30). Outer layer 32 may be formed by extruding a thirdpolymer material about the matrix material layer 30. In some embodimentsof the invention, outer layer 32 and matrix material layer 30 areco-extruded about braided wire mesh assembly 28. In other embodiments ofthe invention, outer layer 32 may be separately extruded and thenslipped about matrix material layer 30, such as illustrated in FIG. 2.

Outer layer 32 is typically a melt-processable polymeric tube, such asan extruded polytetrafluoroethylene (PTFE) tubing (e.g., Teflon® brandtubing), optionally with surface chemical etching. One of ordinary skillwill appreciate that outer layer 32 may also be made of othermelt-processable fluoropolymers, including, without limitation,fluorinated ethylene-propylene copolymer (FEP), perfluoroalkoxyethylene(PFA), poly(vinylidene fluoride), poly(ethylene-co-tetrafluoroethylene),and the like with surface treatment. Outer layer 32 may also be made ofmelt processable thermoplastic elastomers with sufficiently highmechanical strength and rigidity, including, without limitation,polyamide-based thermoplastic elastomers (namelypoly(ether-block-amide), Pebax®), polyester-based thermoplasticelastomers (e.g., Hytrel®), thermoplastic polyurethanes (e.g.,Pellethane®, Estane®), and the like, and any combinations thereof. Ingeneral, outer layer 32 may also be made of thermoplastics selected fromthe group consisting of polyamides, polyurethanes, polyesters,functionalized polyolefins, polycarbonate, polysulfones, polyketones,liquid crystal polymers, functionalized polyolefins, and any combinationthereof. Specific suitable materials for outer layer 32 include, withoutlimitation, Pebax® 7233 and Pebax® 6333, Grilamid L25, Rilsan AESNO,Rilsan BESNO, Makrolon 3108, and the like. One of ordinary skill in theart will readily appreciate that the third material of outer layer 32may be different from or substantially identical to the first materialof inner layer 26 as desired, and will further appreciate how to selectsuitable materials for inner layer 26 and outer layer 32 for aparticular application of catheter 10.

Typically, matrix material layer 30 will be different from at least oneof the first material forming the inner layer 26 and the third materialforming the outer layer 32. Matrix material layer 30 is preferablyhyperelastic relative to either inner layer 26 or outer layer 32, and,in some embodiments, matrix material layer 30 is hyperelastic ascompared to both inner layer 26 and outer layer 32.

It is desirable for there to be at least partial chemical compatibilitybetween matrix material layer 30 and inner layer 26 and outer layer 32.This will promote inter-layer bonding between the layers of the cathetershaft assembly and reduce the likelihood of strain-induced polymerdelamination under manipulation of catheter 10. Such compatibility maybe provided by forming inner layer 26 and outer layer 32 of materialswhose polarity and/or solubility parameter are similar to that of matrixmaterial layer 30. Alternatively, or additionally, chemicalmodifications may be undertaken to achieve at least partial chemicalcompatibility between layers (e.g., blending and compounding matrixmaterial layer 30 with a minor amount of the material of inner layer 26or outer layer 32). Alternatively, surface modifications on one or moreof the layers can also promote inter-layer bonding.

In some embodiments of the invention, it is desirable for the cathetershaft assembly to be radiopaque. Thus, it is contemplated that one ormore of inner layer 26 and outer layer 32 may include a radiopaquefiller. Suitable radiopaque fillers include, without limitation, bariumsulfate, bismuth subcarbonate, bismuth trioxides, bismuth oxychloride,tungsten, tantalum, platinum, gold, and any combinations thereof.Radiopaque nanoclays may also be employed. Typically, matrix material 30will not include such radiopaque fillers, but doing so is not outside ofthe spirit and scope of the present invention. As an alternative to theuse of radiopaque fillers, or in addition to the use of radiopaquefillers, a radiopaque marker (not shown) may be included in the cathetershaft assembly.

FIG. 2 displays an axial-cross section of the catheter shaft assemblyincluding mandrel 24, inner layer 26, braided mesh assembly 28, matrixmaterial layer 30, and outer layer 32 before thermal lamination of thevarious layers by heating (e.g., reflow bonding). FIG. 3 depicts alongitudinal cross-section of the catheter shaft assembly at the samestage of manufacture. In some embodiments of the invention, a layer ofheat shrink 34 is placed over outer layer 32 as depicted in FIGS. 2 and3. Heat shrink 34 is preferably a fluoropolymer such as fluorinatedethylene-propylene copolymer (FEP). As an alternative to heat shrinktube 34, the catheter shaft assembly may be placed into a suitable moldprior to subsequent processing. Either heat shrink tube 34 or a suitablemold may be generally referred to as a “shape retention structure,” sonamed because it retains the overall shape of the catheter shaftassembly (that is, the generally circular axial cross-section) duringmelt-processing.

As shown in FIG. 4, the catheter shaft assembly may then bemelt-processed. Energy (e.g., radiofrequency energy or thermal energy)is applied to the catheter shaft assembly, for example to the outersurface of the catheter shaft assembly, to bond inner layer 26, matrixmaterial layer 30, and outer layer 32 (if present) together in a processoften referred to as “reflow bonding.” Heat shrink tube 34 has a highermelting or softening temperature than inner layer 26, matrix materiallayer 30, and outer layer 32, such that, during the melting process,heat shrink tube 34 will maintain its tubular shape and/or contractduring the reflow process. The combination of applied energy andpressure exerted by heat shrink tube 34 forces melted inner layer 26,matrix material layer 30, and outer layer 32 to flow locally andredistribute about the circumference of the catheter shaft assembly andmelt together, as represented by interphase lines 36 a (between innerlayer 26 and matrix material layer 30) and 36 b (between outer layer 32and matrix material layer 30).

Once the catheter shaft assembly has cooled, mandrel 24 can be removed,leaving a central lumen 38 (FIG. 5) extending through at least a portionof catheter shaft 12. Optionally, heat shrink tube 34 may also beremoved, such that outer layer 32 becomes the outermost layer of thecatheter shaft assembly.

FIG. 5 depicts the catheter shaft assembly after the conclusion of thereflow bonding process (that is, FIG. 5 depicts an axial-cross sectionof a catheter shaft formed according to an embodiment of the presentinvention). One of skill in the art will appreciate that, as a result ofthe reflow bonding process described above, matrix material layer 30will flow and impregnate braided mesh assembly 28, such that braidedmesh assembly 28 will be at least partially embedded within matrixmaterial layer 30. In the preferred embodiments of the invention,braided mesh assembly 28 will be fully embedded within matrix materiallayer 30 (that is, without gaps or protrusions out of the inner or outersurface boundary of matrix material layer 30). The term “embedded” isused herein to describe both partially embedding and fully embeddingbraided mesh assembly 28 within matrix material layer 30. This isdepicted in FIG. 5 as plait matrix layer 40.

As described above, plait matrix layer 40 is hyperelastic relative to atleast one of inner layer 26 and outer layer 32 as a result of the use ofmatrix material layer 30. This hyperelasticity permits braided meshassembly 28 to adjust its deformed conformations by introducingrelatively large localized material strains (e.g., localized opening andclosing of the braid plaits) within plait matrix layer 40 with a reducedrisk of concomitant material failure (e.g., material yielding andtearing). Similar strain adjustments will take place at the interphaseof plait matrix layer 40 and inner layer 26 and the interphase of plaitmatrix layer 40 and outer layer 32 when catheter shaft 12 is subjectedto bending, flexing, tension, compression, or any combination of suchloads. Thus, a catheter shaft according to the present inventionexhibits improved mechanical integrity even if the load exceeds theyield strain of either or both of inner layer 26 and outer layer 32.Moreover, the hyperelasticity of plait matrix layer 40 will tend to“drive” braided mesh assembly 28 to “quasi-elastically” recover itsundeformed conformation, even if the load exceeds the yield strain ofeither or both of inner layer 26 and outer layer 32. In sum, thehyperelasticity of plait matrix layer 40, along with its lessenedconstraints upon braided mesh assembly 28, improve the kink resistanceand mechanical integrity of a catheter shaft constructed according tothe present invention.

As described above, the plaits within braided wire mesh assembly 28 mayadjust their conformations as catheter shaft 12 is maneuvered (e.g.,pushed, torqued, and flexed), thereby introducing localized strainredistributions inside plait matrix layer 40. Therefore, it iscontemplated that braided wire mesh assembly 28 may be coated, forexample with silicone, to form thin polymeric films on braided wire meshassembly 28 and facilitate the spring-like hyperelastic recoveryperformance of plait matrix layer 40 as described above.

In one exemplary embodiment of the invention, both inner layer 26 andouter layer 30 are formed of Pebax® 7233 filled with 40% barium sulfatefillers and matrix material layer 30 is formed of Pebax® 4033.

In another exemplary embodiment of the invention, one of inner layer 26and outer layer 30 is formed of Pebax® 6333 filled with 40% bariumsulfate fillers and the other of inner layer 26 and outer layer 30 isformed of Pebax® 7233 filled with 40% barium sulfate fillers. Matrixlayer 30 is formed of Pebax® 4033.

In yet another exemplary embodiment of the invention, inner layer 26 isformed of Makrolon 1239, matrix layer 30 is formed of Pebax® 4033, andouter layer 32 is formed of Pebax® 6333 filled with 40% barium sulfatefillers. Alternatively, outer layer 32 may be formed of Pebax® 7233filled with 40% barium sulfate fillers.

In a further exemplary embodiment of the invention, inner layer 26 isformed of Makrolon 1239, matrix layer 30 is formed of Surlyn 9320, andouter layer 32 is formed of Pebax® 7233 filled with 40% barium sulfatefillers.

Although several embodiments of this invention have been described abovewith a certain degree of particularity, those skilled in the art couldmake numerous alterations to the disclosed embodiments without departingfrom the spirit or scope of this invention. For example, a catheterformed according to the present invention may have varying sizes andvarying uses, including, but not limited to, the treatment of atrialfibrillation and the treatment of atrial tachycardia.

One of ordinary skill in the art will also appreciate that othermodifications could be made to the catheter shaft assembly hereinwithout departing from the spirit and scope of the present invention.For example, the catheter shaft assembly could be made steerable, forexample as described in U.S. application Ser. No. 11/647,313, filed 29Dec. 2006 (“the '313 application”), or with embedded internalcomponents, for example as described in U.S. application Ser. No.11/646,578, filed 28 Dec. 2006 (“the '578 application”). Both the '313application and the '578 application are hereby incorporated byreference as though fully set forth herein.

In addition, it is contemplated that a catheter according to the presentinvention may be manufactured using alternative techniques. For example,rather than bonding the layers of the catheter shaft assembly viamelt-processing (e.g., reflow bonding) as generally described above, oneor more layers may be extruded over one another (e.g., extrusion ofmatrix material layer 30 over braided mesh assembly 28). Where one ormore layers are extruded, they may be coextruded (e.g., coextrusion ofmatrix material layer 30 and outer layer 32). Of course, it is alsowithin the spirit and scope of the invention to utilize a combination ofreflow bonding and extrusion processes (e.g., reflow bonding matrixmaterial layer 30, braided mesh assembly 28, and inner layer 26,followed by extrusion of outer layer 32 thereabout). As another example,the various polymeric layers may be formed by wrapping or winding asuitable material about the catheter shaft assembly (e.g., wrappingsurface-etched PTFE tape about mandrel 24 to form inner layer 26).

All directional references (e.g., upper, lower, upward, downward, left,right, leftward, rightward, top, bottom, above, below, vertical,horizontal, clockwise, and counterclockwise) are only used foridentification purposes to aid the reader's understanding of the presentinvention, and do not create limitations, particularly as to theposition, orientation, or use of the invention. Joinder references(e.g., attached, coupled, connected, and the like) are to be construedbroadly and may include intermediate members between a connection ofelements and relative movement between elements. As such, joinderreferences do not necessarily infer that two elements are directlyconnected and in fixed relation to each other.

It is intended that all matter contained in the above description orshown in the accompanying drawings shall be interpreted as illustrativeonly and not limiting. Changes in detail or structure may be madewithout departing from the spirit of the invention as defined in theappended claims.

1. (canceled)
 2. A method of manufacturing a catheter shaft, comprising:forming a wire reinforcing layer; forming a layer of a first materialabout the wire reinforcing layer and extending along an entire length ofthe wire reinforcing layer; forming an outer layer of a second materialabout the layer of the first material and extending continuously along alength of the layer of the first material, wherein the first material ishyperelastic relative to the second material; and bonding the secondmaterial to the first material such that the wire reinforcing layerbecomes fully embedded in the second material.
 3. The method accordingto claim 2, wherein at least one of the first material and the secondmaterial comprises a melt-processable polymer.
 4. The method accordingto claim 3, wherein both the first material and the second materialcomprise melt-processable polymers.
 5. The method according to claim 2,wherein at least one of the first material and the second materialcomprises a particulate radiopaque filler material.
 6. The methodaccording to claim 2, wherein the wire reinforcing layer comprises abraided wire mesh.
 7. The method according to claim 2, wherein the outerlayer extends along an entire length of the first material.
 8. Acatheter shaft, comprising: a plait matrix layer including a wirereinforcement fully embedded in a first material; and an outer layer ofa second material bonded to the plait matrix layer and extendingcontinuously along a length of the plait matrix layer, wherein the firstmaterial is hyperelastic relative to the second material.
 9. Thecatheter shaft according to claim 8, wherein one of the first materialand the second material comprises a melt-processable polymer.
 10. Thecatheter shaft according to claim 8, wherein the first materialcomprises a first melt-processable polymer and the second materialcomprises a second melt-processable polymer.
 11. The catheter shaftaccording to claim 8, wherein at least one of the first material and thesecond material comprises a particulate radiopaque filler material. 12.The catheter shaft according to claim 8, wherein the wire reinforcementcomprises a braided wire mesh.
 13. The catheter shaft according to claim8, wherein the outer layer extends continuously along an entire lengthof the plait matrix layer.